Predictability is something is something we all try to avoid as writers, but it’s something a lot of writers fall into in a goal to create conflict. Conflict makes stories interesting, so writers try the most common ways to do that and instead end up with an entirely predictable situation.
In dystopian novels, if your characters come across another group, the group will most likely try to kill your characters for supplies. In fantasy novels, the main character is seeking refuge in a farmhouse, and the farmer sells the character out to protect his daughter.
These situations happen over and over again in books, movies, and TV shows, to the point where we expect it to happen.
If I am watching a dystopian post-apocalyptic movie where a guy comes across an old granny calling for help on the road, I know it is going to be a trap. It will not be a surprise. So, what you have to do to actually make your conflict a surprise is to find the perfect balance between good strangers and not so good strangers.
For example, imagine a main character is tired from being on the run from some evil dudes, so he stays in an inn and falls asleep. Well, that is when the bad guys attack. They come up to the inn-keeper and ask her if she has seen the main character. She shrugs and says she does not know; simply because she has a code of protecting her customers. They go to attack her for more information, and old granny the inn-keeper goes crazy on them with an axe.
That would be way more surprising to me than if she had simply said “Don’t kill me! He is upstairs!”
However, this is also a line you have to be careful not to cross. If all the people your main character come across are good, you end up with the same problem as when they are all bad. So, you have to find the perfect balance between the two.
If you do it right and your characters come across a group of strangers, your readers will not know if the strangers are going to turn on the characters and attack because you have set this standard that they might actually be good.